Auto Fan Control setting: Target Fan Speed?

AndreyT wrote: I have an ASRock Z75 Pro3 LGA 1155 board, which offers automatic CPU temperature-based fan speed control in its BIOS settings. When I switch a fan to Automatic mode in BIOS, it asks me to specify two parameters: Target CPU Temperature and Target Fan Speed. My question is: how exactly do these two parameters work together and how do they affect fan speed? What is the meaning of Target Fan Speed parameter? How is Target Fan Speed related to Target CPU Temperature? There's no explanation in the manual.

Before I explain these two parameters, I must list a few requirements that must be met in order for the explanation to apply:

The CPU Fan 1 & 2 Setting option must be set to Automatic. The Automatic setting will increase or decrease the speed of the fans connected to the CPU Fan 1 and 2 headers, depending upon the temperature of the CPU.

The fan used on the CPU Fan 1 header (labeled CPU_FAN1 on the board) must be a four pin, PWM speed controlled fan. A three pin voltage speed controlled fan cannot have its speed controlled on a four pin PWM fan header. Any three pin fan used on this header will run at its maximum speed.

Target Fan Speed is the minimum speed a PWM fan connected to the CPU_FAN1 will operate at.

All fans, whether PWM or voltage speed controlled, operate at different minimum and maximum speeds, and need differing amounts of voltage to start spinning, and maintain a certain speed (RPM.) There are no standards for a fan's maximum speed, minimum speed, start up voltage, and maximum power usage, that are used by PC fan manufactures.

That is why you see the Level settings, from 1 to 9, that allows you to select the minimum speed the fan will operate at. You will need to experiment with the Level settings in order to find one that meets your needs. Normally that is the setting that cools the CPU adequately when it is at idle/low load, and is not so loud it bothers you. You of course can set the minimum fan speed however you prefer.

If you use one of the newer or newest UEFI/BIOS versions, you may also see an entry called Custom Speed. Some ASRock boards with Intel 7 series chipsets have this setting, I don't know if your board's UEFI/BIOS will. Selecting this setting will reveal another option, Custom Fan Speed. That setting is a number from 1 to 255, which again selects the minimum speed the fan will operate at. This option simply provides a wider and finer range of minimum speeds.

Target CPU Temperature is the threshold temperature for automatically increasing the speed of the fans on the CPU Fan 1 and 2 headers.

I must say that in my experience with my ASRock Z77 Extreme4 board, that the Target CPU Temperature does not have much affect. Using the lowest setting, 45C/113F, the CPU Fan 1 and 2 speeds will increase before the CPU temperature reaches 45C. IMO, that is fine. You can experiment with that option if you want to have a quiet PC, and only increase the CPU fan speeds when the CPU temperature is say 60C for example.

A simple way to try different fan speed settings is to install the ASRock Extreme Tuning Utility. Its Fan Control feature provides the same settings as in the UEFI/BIOS. You can change the fan speeds and Target Temperature (but not from Automatic to Full On) to see what you like or for special purposes. These settings do not change the settings in the UEFI/BIOS.

AndreyT wrote: OK, thank you for your reply. So, basically Target Fan Speed stands for baseline fan speed in "low heat" conditions. It would still be interesting to know the algorithm/formula that calculates the speed from the CPU temperature. You are saying that the fan begins to ramp up before the Target Temperature is reached...

Yes, your definition is one way to look at it. But what is your definition of "low heat" conditions? Someone may think anything below 50C is cool enough for a CPU.

Target Fan speed is the minimum speed a PWM fan will run at. Since every PWM fan is different, this setting allows you to tune your fan's speed to a starting point for PWM speed control.

One aspect of PWM speed control (which is used on all stock Intel CPU coolers) is the ability to run the fan at the lowest speed possible to minimize fan noise, while providing adequate cooling. This is only one of many ways to configure PWM fans. You may have a different notion of how you want your CPU cooler's fan to operate, based on your personal usage of a PC, and your tolerance to fan noise.

I agree with the minimum speed for adequate cooling "philosophy". While I type this, my CPU is in a low power state, running at 800MHz. My CPU cooler's fan is running at ~700RPM, and my CPU core temperatures are between 22 - 27C.

If I turn off the CPU power saving options, the cores run at 4.0GHz, and are still basically idling along as I type this, but the core temperatures are now 33 - 35C. The CPU fan speed is up to a bit over 800RPM, as the speed is automatically increased by PWM control.

I'm going by memory since I'm not using my Z77 board PC now. I recall that with the Target CPU Temperature set to 45C (lowest possible), that the fan speed would increase when the CPU was below 45C.

Fan speed control on mother boards is a strange thing. You would think it would have been figured out years ago. The fan speed control on your board is somewhat primitive compared to ASRock's newer products. Another mobo manufacture had the equivalent of ASRocks current fan speed control years ago. Yet another major mobo manufacture I was reading about has its users claiming there is no fan speed control working at all on their latest boards.

Fan speed control on a board, the fans and CPU cooler we use, and noise levels are all variables that result in the need to experiment with what we have to see how it works for us. You need to get a program to monitor the CPU fan speed, and then experiment with A-Tuning's fan speed control in Windows, with different loads on the CPU. That way you can determine what works best for you.

munrobasher wrote: I've just bought a 970M Pro3 motherboard which I'm very impressed with. I'm not so impressed with the stock cooler on the AMD FX 6350 which sounds like a jet engine. Sounds like a jet engine in the living room! So I found this post useful in understanding the overclocking settings so that at least when idle, the fan is just annoying as opposed to unbearable. I've reduced the fan target speed down to 2 but in order for this to make a difference, I've also had to let the CPU temperature got up to 60C (default is 45C) otherwise the target fan speed doesn't make much difference - the stock fan is so crap that it struggles to ever get the CPU temperature down to 45C so runs at a higher speed anyway. I'm going to look at a Cool Master Hyper 212 EVO which should run quieter once I've confirmed it'll fit in the 970 Pro3 motherboard and not foul the high fins on my Corsair Vengence RAM

You've got both a 970M Pro3 and 970 Pro3 boards mentioned in your post, although it makes no difference with the memory clearance and a Hyper 212 EVO, as I said in your thread about the clearance question.

Stock, inbox CPU coolers are notorious for being loud. The smaller the fan they use, the louder they will be, since they must run at high speeds to compensate for the small fan.

Plus there is no standard for a fan's speed at an applied voltage. That's impossible when fans exist in sizes from 20mm to 200mm, or more. A 20mm fan spinning at 500RPM is worthless, not that a 20mm fan at 5,000RPM is much better.

Fan speed control on mother boards attempts to deal with the huge range of fan speed behavior of different fans. But it is virtually impossible to deal with all fans, with one main issue that must be dealt with. That is, particularly for CPU cooler fans, to NOT allow them to not spin at all, at the minimum fan speed setting. A case of protecting the user from themselves, unfortunately.

That's why at even the lowest fan speed setting, small fans on CPU coolers will be whining at 2,000+RPM.

Some older boards I've used, had a "Low CPU Fan Speed" warning that would appear when the PC booted. If the CPU fan was below 500RPM, that warning would appear. Of course the board's BIOS had no idea what fan it was complaining about, and the CPU cooler could be a huge double tower model with two 140mm fans, or a liquid cooled setup with dual fan radiator using four fans in push-pull mode.

My ASRock X99 and Z170 boards have fan speed controls that allows you to set the various fan headers to zero RPM at any CPU temperature below 80C. That's passable for Intel processors, since at 80C the fan(s) will jump to 80% speed automatically. Most of the processors used with these boards aren't supplied with stock CPU coolers, and it is assumed the users know what they are doing... fingers crossed.

DarrylG wrote: I've had a B75M-DGS motherboard for about four years, and this feature has never worked.  No matter what I set it to, the heatsink fan runs at full speed.

What are you using for a CPU cooler?

Where is the CPU cooler's fan connected? To which fan header?

Where are you configuring the CPU coolers fan speed? In the BIOS? In the Windows AXTU program?

What setting(s) are you using for the CPU cooler speed configuration?

Do you use the AXTU program? If so, do you auto-run it when Windows boots?